1. Field of the Invention
The present invention relates to a printing apparatus that forms, by using a plurality of printing apparatuses, an image on a sheet of paper by first toner and second toner, a printing method, and a computer-readable storage medium for implementing the printing method.
2. Description of the Related Art
Recently, there has been offered an electrophotographic apparatus that uses clear toner as a special recording material. The clear toner is a transparent recording material for adding a transmissive image.
The use of the clear toner enables various expressions, adding more values to output products. A mechanism of adding the clear toner in addition to color toner such as cyan, magenta, yellow or black (C, M, Y, or K) is incorporated in one electrophotographic apparatus, that can create an output product using the clear toner. In such an apparatus, however, when a special recording material such as a clear toner is used to perform printing, compared with conventional printing using four-color toner, a total amount of toner used for the printing is much greater.
Especially when applied to electrophotographic color printing, a special recording-material image is formed on an intermediate transfer member in addition to conventional four-color images of C, M, Y, and K, and must be transferred to a sheet.
In each electrophotographic process, an amount of applied toner that is an amount of toner necessary for printing increases. A result is a greater load on each process.
Japanese Patent Application Laid-Open No. 2007-011028 discusses a method for calculating a recordable amount of an applied special recording material from an applied four-color toner amount of C, M, Y, and K.
However, when an amount of an applied special recording material is calculated by the method discussed in Japanese Patent Application Laid-Open No. 2007-011028, the amount of an applied special recording material may be zero. For example, a total amount of applied four-color toner exceeds a total amount of application which can be fixed well on the sheet and is permitted by the printing apparatus.
In such a case, even when a user instructs printing that uses the special recording material, the printing using the special recording material based on the user' s instruction cannot be performed. Thus, no visual effect by the special recording material can be obtained.
To deal with this problem, as discussed in Japanese Patent Application Laid-Open No. 2008-139589, when it is determined that the printing using the special recording material based on the user's instruction cannot be completed by fixing an image once, a method for preparing the special recording material is changed.
More specifically, an image is first printed and fixed by using toner other than the special recording material to output a sheet. The image is then printed and fixed again, by using the special recording material, on the sheet where the image has been printed by using the toner. This printing based on the twice fixing of the image is referred to as two-pass printing.
The use of the two-pass printing enables printing that uses an amount of a special recording material equal to or greater than an amount of a special recording material determined in view of a total amount of application permitted by the printing apparatus. Thus, an output product having a visual effect provided by the special recording material as desired by the user can be obtained.
The incorporation of the mechanism corresponding to the clear toner solves a problem such as a limit on the amount of toner. However, for those who use no clear toner, the mechanism dedicated to clear toner is wasteful in terms of costs or functions.
Thus, a system is configured, which separately includes a printing apparatus using color toner and a printing apparatus using the special recording material, and connects a sheet discharge unit of the printing apparatus using the color toner to a sheet feeding unit of the printing apparatus using the special recording material, thereby generating an output product using the special recording material in a collective manner. For example, for the user who performs printing using the special recording material, the system that interconnects the printing apparatus using the color toner and the printing apparatus using the special recording material is provided. For the user who uses no special recording material, only the printing apparatus using the color toner is provided. Creating such a mechanism of interconnecting two printing apparatuses enables configuration of a system in response to a user's request. However, in the structure where the two printing apparatuses are interconnected to be used, both printing operations stop each time one of the printing apparatuses on a front side and a rear side stalls. As a result, for example, when the printing apparatuses alternately stall, good device performance cannot be achieved as overall performance of the printing system.